Semi-automated liquid chromatography–mass spectrometric imaging platform for enhanced detection and improved data analysis of complex peptides

• A new interface coupling monolithic nano-LC and MALDI MS imaging is developed.
• The LC–MSI device offers enhanced MS signals with accurate relative quantitation.
• Improved data analysis based on either m/z or retention time can be performed.

A semi-automated analytical platform featuring the coupling of monolithic reversed-phase liquid chromatography (RPLC) to matrix-assisted laser desorption/ionization mass spectrometric imaging (MALDI MSI) has been developed and evaluated. This is the first time that LC separation is readily coupled to MS imaging detection for the analysis of complex peptide mixtures both qualitatively and quantitatively. Methacrylate-based monolithic column with C12 functional groups is fabricated for fast RPLC separation. The LC flow and matrix flow are collected on a commercially available MALDI plate which is mechanically controlled and analyzed with MALDI MSI subsequently. Both tryptic peptides digested from bovine serum albumin (BSA) and endogenous neuropeptides extracted from the blue crab Callinectes sapidus are analyzed with this novel LC–MSI platform. Compared with regular offline LC fractionation coupled with MALDI MS detection, LC–MSI exhibits significantly increased MS signal intensity due to retaining of temporal resolution from separation dimension via continuous sampling, which results in increased number of peptides detected and accurate quantitation. In addition, imaging signals enable improved data analysis based on either mass-to-charge ratio or retention time, which is extremely beneficial for the analysis of complex analytes. These findings have demonstrated the potential of employing LC–MSI platform for enhanced proteomics and peptidomics studies.